Lysosomes are cellular structures which function in the catabolism of biological macromolecules. These organelles perform heterophagy, a metabolic sequence whereby a cell engulfs molecules from the extracellular environment by pinocytosis in order to catalyze their degradation within the lysosomes. Lysosomes are also involved in the degradation of intracellular macromolecules and organelles by the process of autophagy. Finally, there are pathologies in which undegraded materials accumulate within the lysosomes. These abnormalities are due to the genetic absence of a lysosomal hydrolase, whose substrate would normally be digested within the organelle. Asialo-glycoproteins, when injected intravenously into a rat, are rapidly removed from the circulation by hepatocytes and then processed through heterophagy. The objects of this project are: (1) to characterize lysosomal degradation of the carbohydrate moiety of glycoproteins, (2) to develop an animal-model for lysosomal storage diseases, and (3) to compare the activities of lysosomes in Kupffer cells and hepatocytes. In order to achieve these goals a combined biochemical and morphological study of the heterophagic processing of N-Acetyl-D-(d-3H) glucosamine-labeled orosomucoid and its derivatives will be made using perfused rat liver and isolated hepatocytes and sinusoidal cells. The radioactive glycoprotein substrate will be obtained by adding D-(6-3H)glucosamine to a perfused rat liver and then isolating the newly synthesized (3H)orosomucoid that is secreted into the perfusate. In other studies the carbohydrate portion of the glycoprotein will be chemically modified so that the molecule resists degradation by the lysosomal hydrolases. These modified glycoproteins should compact the liver lysosomes and the treated tissue will become a model for lysosomal storage disease. This overall project should provide basic understanding of both normal and pathological aspects of lysosomal metabolism.